The invention relates to the fine purification of isophoronediamine (IPDA) using a two-stage column setup comprising a partial condenser and recycling.
The production of IPDA by aminating hydrogenation of isophorone nitrile (IPN) is known and has already been described numerous times.
In the simplest case (U.S. Pat. No. 3,352,913), IPN is reacted in the presence of hydrogen and of an excess of ammonia over a cobalt catalyst. IPN and ammonia initially react with elimination of water to form isophorone nitrile imine, IPNI, which is subsequently hydrogenated to IPDA:

In addition, processes for producing isophoronediamine are known from CN 104230721A, EP 2 649 042A and WO 2012126869A.
In EP 2 649 042A isophoronediamine is produced from isophorone nitrile in a one- or two-stage reaction. Isophorone nitrile is initially iminated with ammonia to afford isophorone nitrile imine. Said isophorone nitrile imine is hydrogenated to afford isophoronediamine in the second step. The purification that follows the reaction is likewise divided into two steps. The low boilers are initially removed in a plurality of distillation columns, said low boilers including hydrogen, inert gases, ammonia and low-boiling impurities (low boiler removal). In a final step the pure isophoronediamine is then obtained via two vacuum distillation columns. The first column in turn serves to remove any remaining relatively low-boiling by-products. In the second column the isophoronediamine is obtained in pure form overhead and thus separated from the organic residues (high boilers).
WO 2015/038679 describes a process for separating ammonia and a diamine. The distillation is effected here by means of a sequence of three distillation columns, wherein ammonia is removed as low boiler overhead in each column.
The two applications EP 1529027 and EP 1529028 describe the fine purification of IPDA by distillation in a setup composed of at least two columns. In this case, there is both removal of low- and high-boiling secondary components and separation into two separate IPDA fractions. These each differ in terms of their cis/trans ratio.